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Show APPENDIX NN. 1305 Below is appended a full list of the Pacific province form? that find their eastern limit along the eastern slope of the main chain.* I. Species limited by eastern slope: 1. Zonotrichia coronata. Fall migrant. 2. Passerella var. megarynoha. Summer resident. 3. Pipilo var. oregonus. Resident. ' 4. Cyanura\ Ar. frontalis. Resident 5. Cyanocitta var. californica. Resident. 6. Picus albolarvatus. Resident. 7. Sphyrapicus ruber. Resident in small numbers; fall migrant. 8. Oreortyx picia. Resident. If. The following Pacific province species find their limit as above in the breeding season, but daring the migrations, especially in the fall, they occur more or less frequently at points at variable distances to the eastward: * 1. Turdus pallasii var. nanus. Migrant. 2. Turdus swainsoni var. ustulatus. Summer resident. 3. t Thryothorus bewickii var. spilunts. Resident. 4. Troglodytes hyemalis var. pacificus. Wiuter resident. 5. Helminthophaga celata var. lutescens. Summer resident. 6. Myiodioctes pusillus var. pileolatus. Summer resident. 7. Melospiza melodia var. heermanni. Resident. 8. Melospiza melodia var. guttata. Perhaps accidental. One specimen in West Ham-boldt Mountains in fall. ( Ridgway.) 9. J unco oregonus. Resident. 10. Zonotrichia leuoophrys var. intennedia. Summer. 11. t Agcelaius phceniceus var. gubernator. Summer. 12. t Kepocates niger. Summer. 13. t Chcetura Vauxii, Summer. 14. Selasphorus rufa. Summer. As noticed above, the fauna of the plains and valleys to the east of the main chain is, in respect to its summer residents, indistinguishable from that of the middle province. As showing the sharpness with which the line of demarkation is drawn by the Sierra Range we are able to note but two species, which may be considered as characteristically belongiug to the middle province, which, in their range westward, intrude beyond the limit assigned and reach into the mountains. These are Carpodacus frontalis and Pica melanoleuca var. hudsonica. The first is numerous about Lake Tahoe, but does not, so far as I could ascertain, reach to the west of the divide. Pica hudsonica scarcely finds its way inte the range, but is mostly limited by the foot- hills. A few individuals, however, were noticed by us on the borders of Tahoe. Of the specimens procured along the eastern slope during the Reason a number have proved of especial interest, as illustrating the differentiation which takes place iu a species or variety when found at a point remote from the locality or region where its peculiarities attain their maximum development, and which consequently may be con* sidered its true home. The eastern slope of the Sierras, though belonging, as has been shown, to the Pacific province, occupies a somewhat intermediate position between the Pacific and Middle provinces, and, as it differs climatically more or less from either regijn, its birds might be supposed to indicate to some extent, in plumage or otherwise, the changes undergone in the conditions of environment. Such has been found to be true. This is best illustrated in the cases of several birds that are represented by different varieties in the two provinces. In all such instances, while they are seen to partake more largely of the characteristics pertaining to the Pacific forms, they are yet, to a very appreciable extent, intermediate, and, when compared with their respective types from the west coast, will be seen to divaricate directly toward the conditions distinguishing the middle province forms. Thus the Califorman jays ( Cyanocitta floridana var. caltfornica) of the eastern slope not only have smaller bills and feet than coast examples, but their colors throughout are decidedly lighter, thus approaching in characteristics the var. tcoodhousei of the interior, which iu its typical form begins to occur only in the eastern part of Nevada. Similar differences, though not carried to the same extent, are found in the Steller's jay, in the variety known as var. frontalis, which, though confined to the Sierras, becomes somewhat lighter colored, with smaller bill, at its eastern limit than in the Californian coast range on the west. • For a number of these, as well as for indications of the character of their occurrence, I am indebted to the admirable list of Mr. Ridgway; vide Bull. Essex Institute, vql. 6, No. 10; vol. VII, Nos. 1 and 2; and also in several instances to verbal notes furnished by him. t These three birds breed in the valleys adjoining the mountains. |
